Variable silage quality needs balancing

Careful rationing will be needed to offset increased feed prices and to make the most of higher milk prices, as early grass silage analyses are disappointing and variable.

The first 600 grass silages analysed by Frank Wright Trouw Nutrition International for the 2008 crop show a similar analysis to last year, with generally disappointing feed values and considerable variations in results.

Overall results are reasonable, but not exceptional, says Frank Wright ruminant specialist, Rachel Fowers. “Preservation indicators are suggesting well-made silage, but that grass was possibly not in optimal condition,” she says.

“On average the main cutting date was one week later this year than in 2007 and this means many crops may have been over mature leading to reductions in digestibility and energy levels.”

Dairy Group senior nutritional consultant Chris Savery agrees digestibility may be affected due to the delay for some in silaging, and that local weather patterns mean silage quality is wide-ranging. “Some producers will be seeing a lower DM than they would have hoped for, as grass was probably wetter than anticipated,” he says.

Analysis from the first samples from Frank Wright show an average dry matter of 30.8% compared with 30.4% in 2007 and 33.7% in 2006. And it is expected this value may drop as later cut crops are added to the average, predicts Ms Fower.

The “D” value is the same as last year at 67% giving an average energy content of 10.8MJ/kgDM. Crude protein is the same as in 2006 and 2007 at just over 13%.

The Feed into Milk Intake potential is higher this year, 96 compared to 95 in 2007, suggesting cows will be keen to eat the silage, which will be important if intakes are to be maximised to allow a saving in purchased feed.

Despite results not being great, yields are good for this year due to the mild, wet summer, says Mr Savery. “If better digestibility can be achieved in the second cut, then, hopefully, bought-in feed can be minimised,” he says.

Despite some poor values, one parameter that is substantially higher than 2007 is nutrient detergent fibre (NDF), which stands at 50.8% compared with 47.2%, adds Ms Fower.

“NDF is a measure of cellulose, hemi-cellulose and lignin. The higher NDF level this year tends to be associated in particular with increase levels of rapidly fermentable carbohydrate, which can impact on levels of acidosis,” she says.

“The conclusion from the results is that most farmers will be unable to reduce purchased feed levels markedly over last year and rations will need careful formulation to ensure total energy content is high enough and that protein balanced is maintained,” she adds.

Frank Wright calculates a cow yielding 35 litres and offered ad-lib grass silage will require 11kg concentrates a day. “And with milk prices still showing signs of recovery, many farmers will be looking to push yields, but will need to make sure it is done economically,” says Ms Fower.

Early results are generally a reliable indicator of the feed value of the overall crop, she adds. “We would advise farmers to have their silage analysed before making decisions about buying supplements. Armed with an analysis, they will be far better placed to make the correct decisions about the type and quantity of supplements required.”

Dairy event and Livestock show – Free silage analysis
	Farmers who have yet to have their silage analysed can take advantage of free analysis at the Dairy Event and Livestock Show, Stoneleigh, on 17 and 18 September. The silage clinics are returning to the event again this year and the organisers are advising farmers intending to bring samples to take them to the clinics early, as analysis will be offered on a first-come, first-served basis.